The invention relates to an induction furnace for melting and casting substances in a nonreactive atmosphere, having a vacuum-tight furnace chamber with an opening and a closure plate associated therewith, behind which there is disposed a tiltable crucible which has a pouring spout and is surrounded by at least one induction coil, and in which there is also a rotary lead-through carrying current feeders and coolant tubes for the induction coil.
In an induction furnace of this kind, disclosed in U.S. Pat. No. 4,331,828, rotary lead-through is situated in a swinging furnace door and it carries on a unilateral or cantilevered bearing both the melting crucible and the induction coil surrounding the latter. The door is thus subjected to additional stress by twisting forces which have an adverse influence on the sealing of the door against the furnace chamber. Furthermore, the rotary lead-through, which in the final analysis is the single support for the crucible and the induction coil, is also subject to tilting forces which endanger the seal which is extremely necessary at this location. The known furnace is consequently suitable only for melting relatively small amounts of material, and the use of sliding contacts for feeding the coil current leads to the same conclusion. Only the coolant water feeding is performed through hoses and a hose drum which in turn is joined to rigid pipes which are brought through the rotary lead-through. The known arrangement is therefore suitable only for supplying a no more than two-part induction coil. Also, the couplings for the water and power lines to the induction coil are inside of the furnace chamber, so that any leakage during vacuum operation results in serious disturbances of operation.
The task of producing a nonreactive atmosphere in such an induction furnace includes vacuum operation, operation under shielding gas at standard pressure, and under protective gas at a subatmospheric pressure.